Forming apparatus and method

ABSTRACT

An apparatus for and method of forming a sheet metal blank is provided and includes a first die member having an outside forming surface and a second die member having an inside forming surface adapted to cooperate with the outside forming surface to form a workpiece interposed therebetween upon relatively moving the die members along a forming path into operative association. One of the die members is movable transverse such path enabling the forming surfaces acting through the workpiece to precisely align the one member to a forming position and thereby assure precise forming of the workpiece during the operative association.

1 1 Oct. 30, 1973 FORMING APPARATUS AND METHOD [75] Inventor: Daniel F. Cudzik, Richmond, Va.

[73] Assignee: Reynolds Metals Company,

Richmond, Va.

22 Filed: Feb. 8, 1972 21 Appl. No.: 224,566

[52] US. Cl. 72/347, 113/1 F, 72/465 [51] Int. Cl B21d 22/06 [58] Field of Search 72/347, 348, 465, 72/466; 113/1 F [5 6] References Cited UNITED STATES PATENTS 353,188 11/1886 White 72/465 2,389,974 11/1945 72/465 3,344,647 10/1967 113/120 3,585,838 6/1971 72/465 2,177,027 10/1939 113/1 F 1,857,628 5/1932 Eisenlohr 72/427 FOREIGN PATENTS OR APPLICATIONS 724,251 2/1955 Great Britain 72/349 Primary Examiner-Richard J. Herbst Attorney-John F. C. Glenn et a].

[57] ABSTRACT An apparatus for and method of forming a sheet metal blank is provided and includes a first die member having an outside forming surface and a second die member having an inside forming surface adapted to cooperate with the outside forming surface to form a workpiece interposed therebetween upon relatively moving the die members along a forming path into operative association. One of the die members is movable transverse such path enabling the forming surfaces acting through the workpiece to precisely align the one member to a forming position and thereby assure precise forming of the workpiece during the operative association.

3 Claims, 9 Drawing Figures PATENTEDumso 1973 3. 768 2 95 SHEET 1 UF 4 I PAIENTEnncIaolszs 3768295 SHEET 3 [IF 4 There are numerousapparatus and methods in current used which are employed to form workpieces such as fiat sheet metal blanks to define container closure members for metal cans, and the like. However, these apparatus and methods usually employ complicated and expensive components and procedures in order to assure precise formingof each workpiece under allnorma] operating conditions. For example, it has been found that present forming apparatus may be adjusted to'provide acceptable performance initially while com ponents thereof are at normal ambient temperatures, but once these components become heated by normal operation or wear suchapparatus provide poor or marginal performance which often cannot be corrected even by time-consuming, and hence expensive, resetting of the relative positions of cooperating components. It has also been found that even by holding dimensional tolerances of these cooperating components within a few ten-thousandths of an inch, the sameproblems recur due to the above-mentioned wear and heating. The heatingbecomes very difficult to cope with because it results in different and changing unpredictable temperature levels and hence unpredictable dimensional changes of components and their relative positions.

SUMMARY This invention provides a simple and economical apparatus for and method of forming a workpiece such as a sheet metal blank to define a container component such as an end closure, for example, which overcomes the deficiencies and problems of present apparatus and methods. In particular, the apparatus employs a first die member having an outside forming surface and a second die member having an inside forming surface adapted to cooperate with the outside forming surface to form a workpiece interposed therebetween upon relatively moving the die members along a forming path into operative association. One of the die members is movable transverse said path in an essentially free floating manner enabling the forming surface acting through the workpiece to precisely align the one member to a forming position and thereby assure precise forming of such workpiece duringthe operative associatlon.

Other details, uses, and advantages of this invention.

will become apparent as the following description of the exemplary embodiment thereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS member in the upper die set and a second die member. in the lower die set cooperating to align the second die member and certain components thereof in a precise forming position so that the axes of such die members coincide enabling fixing of the second die member and its die set in such precise forming position;

FIG. 3 is a view similar to FllG. 2 illustrating the upper and lower die sets apart and with the lower die set now fixed in its precise positon to enable formingof an associated workpiece;

FIG. 4 is a view with parts in cross section and parts broken away illustrating another exemplary embodiment of the apparatus and method of this invention which employs a free floating die member in its lower die set and showing such die member displaced from its precise forming position;

FIG. 5 is a view similar to FIG. 4 illustrating the die members and die sets of FIG. 4 in operative association with the free floating die member in its forming position and a formed workpiece positioned between the die sets;

FIG 6 is a view, minus the sheet metal web, taken on the line 6-6 of FIG. 4;

FIG. 7 is a perspective view illustrating a typical end closure which may be formed using. either the apparatus of FIG. 1 or of FIG. 4;

FIG. 8 is a view of the apparatus of FIG. 4 drawn to an enlarged scale and particularly illustrating the free floating die member and associated components comprising the lower die set of such apparatus; and

FIG. 9 is a view similar to FIG. 8 illustrating another exemplary embodiment of the apparatus and method of this invention.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS Reference is now made to FIGS. 1-3 of the drawings which illustrate one exemplary embodiment of the apparatus and method of this invention, which is designated generally by the reference numeral 20. The apparatus 20 is particularly adapted to be used in an associated conventional forming press to shear circular planar workpieces in the form of blanks from a sheet metal web 21 and precisely form each blank or workpiece to define container means or a container construction which in this disclosure is in the form of an end closure 22.which is illustrated in FIG. 7.

The end closure 22 is adapted to be fixed in position on an associated container such as a right circular cylindrical can and such closure may be made of any suitable material, such as metal containing aluminum. The exemplary closure 22 has a substantially planar sheetlike central portion 23 and a peripheral fastening flange 24 of conventional construction which enables the closure 22 to be readily fixed in position in a conventional manner.

The apparatus 20 comprises an upper die set which is designated generally by the reference numeral 25, see FIG. 1, and such die set is fixed to a top support structure or support 26. in a manner which will be apparent fromthe following description. In particular, the die set 25 has a supporting ring 27 which has an externally threaded upper portion 28 which is threadedly received within a threaded opening 29 provided in the support 26 and the ring 27 has a shoulder which engages a cooperating projection on a punch adapter or member 31, as illustrated at 30, to hold member 31 against support 26. The upper die set 25 has a forming punch 32 which is suitably fixed to the adapter member 31 by a plurality of threaded bolts 35 and a punch shell 33 is fixed in position concentrically around the forming punch 32 by a plurality of threaded bolts 34.

The upper die set 25 includes a knockout assembly comprised of an inverted lower cup-like member 36 which has a top wall 37 provided with diametrically opposed openings 38 which allow upper extensions 41 comprising the forming punch to extend therethrough 46 is provided and acts between member 44 and a sleeve 47 which is fixed to the top support 26. The spring 46 urges the rod 43 upwardly and simultaneously holds the lower cup-like member 36 in position, as illustrated in FIG. 1

The lower member 36 has an annular bottom surface 50 which is particularly adapted to engage the peripheral portion of a workpiece during the forming thereof. Once the workpiece has been formed defining closure 22 the knockout assembly is actuated, in a manner to be described subsequently, causing surface 50 to engage the closure 22 and remove it from the die set 25.

The upper die set 25 has a stripper retainer 51 which has a threaded inside portion 52 which threadedly engages cooperating outside threads 53 comprising the lower portion of member 27. The retainer 51 retains a stripper 54 for vertical sliding movements and the stripper 54 is used to strip or hold the web 21 away from the upper die set 25 once a circular blank used to define closure 22 has been punched therein. The stripper 54 is supported within an annular chamber 55 defined in part by the outside cylindrical surface 56 of the punch shell 33 and the inside cylindrical surface 57 of the retainer 51.

The stripper 54 has an upper annular heat portion 58 provided with a pair of grooves each supporting an associated O-ring 60. One of the O-rings 60 provides a seal between the stripper 54 and the surface 56 while the other larger O-ring 60 provides a seal between the stripper 54 and the surface 57 as the stripper moves upwardly and downwardly within its chamber 55.

The stripper 54 is resiliently urged outwardly by a fluid such as air under regulated pressure provided through a passage 61 which communicates with the upper portion of chamber 55. The passage 61 is suitably connected to a source of pressurized fluid and flow is provided into chambe 55 in timed sequence as determined by the operating cycle of the machine using apparatus 20.

The upper die set 25 and the die member or forming punch 32 have a common central vertical axis 62 and all components of die set 25 are fixed so that movements transverse axis 62 are not possible. However, the die set 25 is movable parallel to, actually essentially along, the vertical axis 62 (which will later be described as a forming path) by moving the entire top support 26 and this movement may be achieved by attaching the support 26 to a reciprocable component such as an actuator (not shown) of a standard forming machine or press and operating such actuator and press together with the remainder of the apparatus 20, which is also installed in such press and as will now be described.

The apparatus 20 also has a lower die set which is designated generally by the reference numeral 65 and such die set is adapted to be supported on an associated lower fixed support 66 which may comprise the bed of the above-mentioned forming press. The support has an opening or recess 67 provided therein which has a bottom surface 68 which is substantially larger in area than the bottom surface area of the die set 65 to be supported thereon whereby the die set may be shifted around within the opening 67 in an unobstructed manner and for reasons which will be apparent hereinafter.

The lower die set 65 has a bottom adaptor or supporting plate 70 and a lower forming die 71, including a die core 72, are suitably fixed to plate 70 by a plurality of threaded bolts 73. The die set 65 also has a draw ring 74 arranged concentrically around the forming die 71 and the ring 74 is axially movable relative to the forming die 71 and substantially vertically upwardly and downwardly along a central vertical axis 75 which is common to the lower die set 65 and the forming die 71.

The draw ring 74 is supported by conventional presdownwardly against the constant pressure applied bythe pressure pins 76 and in accordance with standard forming practice to enable forming of the closure 22. The lower die set 65 also has an outer ring 77 which is supported concentrically outwardly of the draw ring 74 and the draw ring 77 has an annular insert ring 80 which has a comparatively sharp inner cutting edge 81. The cutting edge 81 cooperates with a sharp outer cutting edge 88 of the punch shell 33 to sever a circular workpiece or blank from the web 21 once the upper die set 25 is moved into engagement with the lower die set 65 and such workpiece is indicated by dotted lines in FIG. 1 and designated by the reference letter W.

The forming die 71 is fixed to the supporting plate 70 in a rigid manner so that it can move only with such plate; however, the plate 70 and the outer ring 77 have a smaller cross-sectional area than the corresponding cross-sectional area of the recess 67 in the fixed support 66. In addition, the plate 70 and ring 77 have a plurality of sets of comparatively large diameter bores 82 and 83 respectively which extend therethrough in aligned end-to-end relation and each set of bores 82 and 83 is adapted to receive an associated threaded bolt 84 of a comparatively smaller diameter than the diameter of such bores. Each bolt has a threaded lower end 85 which is threadedly received in an associated threaded opening 87 in the fixed support 66. With this arrangement, it will be appreciated that by threading each bolt 84 outwardly to the dotted line position illustrated at 86 in FIG. 1, the plate 70, ring 77, and the entire associated structure carried thereby are free to move in a direction transverse the vertical axis 75 and for a purpose to be subsequently described.

To assure that the plate 70 and hence the entire lower die set 65 is free to move within the recess 67 in what may be considered a free floating manner, a comparatively large cutout 89 is provided in the support 66 to receive the head of an associated threaded bolt 73.

Likewise, a comparatively large diameter bore 90 is provided in the plate 70 for receiving each associated pressure pin 76 to assure movement of plate 70 without obstruction by the pressure pins 76.

The die member of forming punch 32 has an outside forming surface 92 which is this example has a substantially frustoconical configuration and terminates in an arcuate lower edge 93. The die member or forming die 71 has an inside forming surface 94 which is adapted to cooperate with the outside forming surface 92 to form a workpiece in the form of a circular blank cut from web 21 upon relatively moving the die sets 25 and 65 and hence die members 32 and 71 into operative association.

Having described the detailed construction and arrangement of the cooperating components comprising the apparatus the detailed description will now pro ceed with a description of the manner in which a workpiece may be formed utilizing such apparatus and method to define a container closure 22. In particular, the web 21 is interposed between the die sets and 65 with lower die set 65 being supported within recess 67 of the fixed support with its threaded bolts 84 loosened as indicated by the dotted line position illustrated at 86 in FIG. 1 whereupon the lower die set and its forming die 71 are free to float in a direction transverse, i.e., perpendicular in this example, to the longitudinal axis 75 of the lower die set 65 and forming die 71 and because axis 75 is arranged parallel to axis 62 die 71 and set 65 are free to float transverse axis 62.

The die sets are then relatively moved together and in this example such relative movement is achieved by moving only the upper die set 75 in what may be considered, as mentioned earlier, the forming path along axis 62 and toward the lower die set 65 causing a workpiece to be sheared between the edges 81 and 88 of members 80 and 33 respectively. Continued movement of the upper die set 25 and its forming punch 32 along the forming path 62 brings the die members 32 and 71 into operative. association. In particular, the frustoconical outside forming surface 92 of punch 32 operatively associates with the inside forming surface 94 of the forming die 71 resulting in the forming die 71 and the entire die structure 65 being precisely aligned so that the forming die 71 is in a desired optimum forming position wherein the axes 62 and 75 coincide (see FIG. 2 of the drawings) and thereby assuring precise forming of the workpiece during the operative association. The movement of die 71 is such that the eccentric displacement E shown in FIG. 1 between axes 62 and 75 is eliminated. Once this forming position has been established the threaded bolts 84 are firmly threaded in position fixing the forming die 71 and lower die set 65 so that the upper die set 25 may be raised to the position shown in FIG. 3.

The upper die set 25 is raised or lifted by raising the entire support 26 whereupon a mechanical cam or other suitable device (not shown) comprising the press having apparatus 20 installed therein engages the head 45.causing member 36 of the knockout assembly to engage the formed closure member 22 and assure removal of such closure member form within the upper die set. Simultaneously with the raising of die set 25 the pressure pins 76 return the draw ring 74 to its raised position whereupon the apparatus 20 is now ready to produce closure members 22 in a high production manner. As operation of the press and apparatus is continued certain ones of the cooperating forming components may wear more than others or certain components may become excessively heated causing slight dimensional changes in cooperating relationships. In the event any of these things occur, it is a simple matter to release the die set 65 by partially unthreading bolts 84 and allowing the forming punch to realign the forming die 71 of the hot apparatus or assembly as described earlier.

Another exemplary embodiment of the apparatus and method of this invention is illustrated in FIGS. 4-6 and 8 of the drawings. The apparatus illustrated in FIGS. 4-6 and 8 is very similar to the apparatus 20; therefore, such apparatus will be designated generally by the reference numeral 20A and parts thereof which are very similar to corresponding parts of the apparatus 20 will be designated by the same reference numeral as in the apparatus 20 also followed by the letter designation A and not described again. Only those component parts which are substantially different from parts of the apparatus 20 will be designated by a new reference numeral also followed by the letter designation A and described in detail.

The apparatus 20A has an upper die set 25A which is identical to the upper die set 25 of the apparatus 20 whereby the only differences are in its lower die set 65A. In particular, the lower die set 65A has a supporting plate A and an outer ring 77A which are suitably held in a fixed position within an opening 67A in the fixed support 66A by threaded bolts 84A and the construction and arrangement of the lower die set 65A is such that the plate 71A and ring 77A are held in such fixed position and in alignment with the upper die set 25A so that the cutting edge 88A of the punch shell 33A is in alignment with the cutting edge 81A of the ring 80A to enable a flat circular blank or workpiece to be cleanly severed from the web 21 once the die sets 25A and 65A are moved into cooperating engagement. It will be appreciated that the dimensional tolerance build-up and the manner in which the die sets 25A and 65Aare fixed in aligned relation are sufficiently precise to allow efficient severing of each blank between the cutting edges 81A and 88A, notwithstanding the fact that it is desired that the operative association of the forming dies 32A and 71A must be controlled in a more precise manner.

However, in the apparatus 20A it is also desired to provide one of the die members, the die member 71A of the lower die set 65A, so that it moves in an essentially free floating manner transverse the forming path defined by moving die set 25A along its axis 62A and the construction of the lower die set 65A is such that only the forming die 71A with its inside forming surface 94A is readily movable in a free floating manner.

In particular, it will be seen that the plate 70A has a top supporting surface 97A which is adapted to support the forming die 71A thereon for horizontal movement transverse the forming path 62A. However, the die member 71A has suitable means holding such member against movements parallel either its central axis 75A or axis 62A, which has been referred to as the forming path (also see FIG. 8) and such holding means will be described now.

The plate 70A has a right circular cylindrical opening or bore 100A extending therethrough which defines a cylindrical surface also designated 100A and the bore is provided with a counterbore 101A which extends upwardly from the bottom surface of the plate 70A and defines an annular bottom retaining surface 102A. The die member 71A has a right circular cylindrical projection 103A provided as an integral part thereof which extends through the bore 100A and the projection 103A has an outside surface 104A which has a substantially smaller diameter than the diameter of the bore 100A for reasons which will be apparent from the following description.

The lower die set 65A has a retainer in the form of a retainer disc 105A which is detachably fixed to the integral projection 103A of member 71A by a plurality of threaded screws 106A and the retainer 105A has a diameter which is smaller than the diameter of the counterbore 101A and larger than the diameter of the bore 100A. Once the retainer 105A is attached against projection 103A, it defines an annular top bearing surface 107A which slidably engages the retaining surface 102A. Thus, the retainer 105A allows movement of the die member 71A in what could be considered a free floating manner while its annular bearing surface 107A prevents movement of the die member 71A along axis 75A and away from the supporting plate 70A.

The lower die set 65A also has resilient means in the form of an annular ring 111A which may be made of a compressible resilient elastomeric material such as polyurethane, a suitable natural or synthetic rubber compound, or the like. The ring 111A is carried in a groove 112A and acts between the surface 100A and surface 104A of projection 103A to roughly position the free floating die member 71A so that it is approximately centered relative to its axis 75A. In the illustration of FIG. 4 the resilient ring 111A is shown roughly positioned or centering the forming die member 71A and the central axis 75A of the forming die 71A is off center or eccentric from the central axis 62A of the upper die set 25A and its forming punch 32A by a distance indicated at E.

During operation of the apparatus A the cooperating arrangement of components is such that initially a blank or workpiece W, shown by dotted lines in FIG. 4, is severed from the web 21 by the edges 81A and 88A of members 80A and 33A respectively whereupon continued relative movement of the die members 71A and 32A toward each other causes the frustoconical forming surface 92A of the forming punch 32A cooperating with the forming surface 94A of the forming die 71A acting through the workpiece to precisely align the member 71A to a forming position where the axes 75A and 62A are in alignment and thereby assure precise forming of the workpiece during the cooperative association of the die sets 25A and 65A and their operating die members 32A and 71A. Thus, regardless of the operating condition of the press and apparatus 20A and regardless of whether the forming components are cold at the beginning of operation or heated after prolonged operation, in each instance a circular blank is severed to define the circular blank or workpiece W and once the members are. moved into operative association the die member 71A freely moves or floats into a precise forming position to assure precise forming of the end closure 22.

Another exemplary embodiment of this invention is illustrated in FIG. 9 of the drawings and this latter embodiment represents a modification of the apparatus and method illustrated in FIG. 4. Therefore, the apparatus and method of FIG. 9 will be designated generally followed by the letter designation M and not described again.

The only difference between the apparatus 20M and the apparatus 20A is that the apparatus 20M does not utilize resilient means, such as the compressible annular ring 111A of apparatus 20A therein, whereby it will be noted that there is a space between the surface 100M and 104M as indicated at 115M; and, it has been found that the apparatus 20M will operate equally well without such annular ring. The apparatus 20 M operates in a substantially identical manner as the apparatus 20A and the forming die 71M moves in a free floating manner on the top surface 97M of its plate M allow ing precise alignment thereof from the eccentric distance indicated at E in FIG. 9 so that once a workpiece is interposed between the die sets 25M and 65M the forming surfaces 92M and 94M acting through the workpiece precisely align the member 71M transverse the forming path or axis 62M to a precise forming position where the centers M and 62M are in precise alignment and thereby assure precise forming of the end closure 22.

The apparatus 20, 20A, and 20M may be employed to form end closures or other cup-shaped articles using any suitable metallic material such as an aluminous material, for example.

Further, to assure precision forming and self centering of the free floating die of a particular apparatus, such as the forming die 71 of apparatus 20, for example, the associated punch shell 33 preferably has an inside arcuate surface 114 which has a radius, see FIG. 1, which is preferably of the order of four times the thickness of the metal stock or web 21 being formed. In addition, the outside top edge of the free floating forming die 71 has an arcuate outer surface 115 which has a radius which may be as small as two times the thickness of web 21. The arcute surfaces 114 and l 15 assure precise forming of each end closure 22 without any tendency for corner-to-corner contact.

In this disclosure of the invention the various actuating means, power sources, means for actuating the knockout device, fluid means for the pressure pins, etc., have not been illustrated. However, it will be appreciated that these items will be provided in accordance with conventional practice well known in the art.

While present exemplary embodiments of this invention and methods of practicing the same, have been illustrated and described, it will be recognized that this invention may be otherwise variously embodied and practiced within the scope of the following claims.

What is claimed is:

1. A forming apparatus comprising, a first die member having an outside forming surface, a second die member having an inside forming surface adapted to cooperate with said outside forming surface to form a flat workpiece interposed therebetween upon relatively moving said die members along a forming path into operative association, one of said members being movable in a fixed horizontal plane transverse said forming path enabling said forming surfaces acting through said workpiece to precisely align said one member to a forming position and thereby assure precise forming of said workpiece during said operative association,

means supporting said one member for movement transverse said forming path, said supporting means comprising a supporting plate having said one member detachably fixed thereto and a support having a recess therein which defines a bottom surface which is larger in area than the bottom surface area of the supporting plate, said bottom surface defining said fixed horizontal plane and slidably supporting said supporting plate and one member fixed thereon with said larger area of said bottom surface allowing said transverse movement, and at least one fastener for fixing said one member and said supporting plate in said forming position in a rigid stationary manner.

2. An apparatus for forming a metal container closure comprising, a first die member having a central axis and a forming surface, a supporting plate held at a fixed position and having a top surface, a second die member slidably supported on said top surface and having a central axis arranged parallel to the central axis of said first die member and having a cooperating forming surface adapted to cooperate with said forming surface of said first die member to form a flat circular workpiece interposed therebetween, said first die member being movable relative to said second die member along a forming path defined by its axis and into operative association with said second die member, said second die member being movable transverse its axis enabling said forming surfaces acting through said workpiece to precisely align said second die member to a forming position wherein said axes coincide and thereby assure precise forming of said workpiece dur ing said operative association, and holding means allowing said transverse movement while holding said second die member against movement parallel to its central axis, said second die member being movable on said top surface in an essentially free floating manner and said holding means comprising a cylindrical bore in said plate, a counterbore extending upwardly from the bottom of said plate and defining a bottom retaining surface between said bore and the maximum diameter of said counterbore, a projection extending downwardly from said second die member and through said bore with a substantial clearance therebetween, and a retainer disc detachably fixed to said projection and having a top bearing surface, said retainer disc allowing movement in said free floating manner with said top bearing surface engaging said bottom retaining surface while preventing movement of said second die member along its axis and away from said supporting plate.

3. An apparatus as set forth in claim 2 in which said projection extending downwardly from said second die member has a right circular cylindrical outside surface, said bore is defined by a right circular cylindrical inside surface having a diameter which is substantially greater than the diameter of the outside surface of said projection, and further comprising resilient means acting between the outside surface of said projection and the inside surface of said bore and serving to roughly position said second die member to a position near said forming position. 

1. A forming apparatus comprising, a first die member having aN outside forming surface, a second die member having an inside forming surface adapted to cooperate with said outside forming surface to form a flat workpiece interposed therebetween upon relatively moving said die members along a forming path into operative association, one of said members being movable in a fixed horizontal plane transverse said forming path enabling said forming surfaces acting through said workpiece to precisely align said one member to a forming position and thereby assure precise forming of said workpiece during said operative association, means supporting said one member for movement transverse said forming path, said supporting means comprising a supporting plate having said one member detachably fixed thereto and a support having a recess therein which defines a bottom surface which is larger in area than the bottom surface area of the supporting plate, said bottom surface defining said fixed horizontal plane and slidably supporting said supporting plate and one member fixed thereon with said larger area of said bottom surface allowing said transverse movement, and at least one fastener for fixing said one member and said supporting plate in said forming position in a rigid stationary manner.
 2. An apparatus for forming a metal container closure comprising, a first die member having a central axis and a forming surface, a supporting plate held at a fixed position and having a top surface, a second die member slidably supported on said top surface and having a central axis arranged parallel to the central axis of said first die member and having a cooperating forming surface adapted to cooperate with said forming surface of said first die member to form a flat circular workpiece interposed therebetween, said first die member being movable relative to said second die member along a forming path defined by its axis and into operative association with said second die member, said second die member being movable transverse its axis enabling said forming surfaces acting through said workpiece to precisely align said second die member to a forming position wherein said axes coincide and thereby assure precise forming of said workpiece during said operative association, and holding means allowing said transverse movement while holding said second die member against movement parallel to its central axis, said second die member being movable on said top surface in an essentially free floating manner and said holding means comprising a cylindrical bore in said plate, a counterbore extending upwardly from the bottom of said plate and defining a bottom retaining surface between said bore and the maximum diameter of said counterbore, a projection extending downwardly from said second die member and through said bore with a substantial clearance therebetween, and a retainer disc detachably fixed to said projection and having a top bearing surface, said retainer disc allowing movement in said free floating manner with said top bearing surface engaging said bottom retaining surface while preventing movement of said second die member along its axis and away from said supporting plate.
 3. An apparatus as set forth in claim 2 in which said projection extending downwardly from said second die member has a right circular cylindrical outside surface, said bore is defined by a right circular cylindrical inside surface having a diameter which is substantially greater than the diameter of the outside surface of said projection, and further comprising resilient means acting between the outside surface of said projection and the inside surface of said bore and serving to roughly position said second die member to a position near said forming position. 